NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 2) (USD $)	3 Months Ended	12 Months Ended					3 Months Ended			3 Months Ended
	Mar. 31, 2013 item	Dec. 31, 2012 item	Mar. 31, 2013 Residential	Dec. 31, 2012 Residential	Mar. 31, 2013 Residential Minimum item	Mar. 31, 2013 Residential Maximum item	Mar. 31, 2013 Residential Single-family	Mar. 31, 2012 Residential Single-family	Dec. 31, 2012 Residential Single-family	Mar. 31, 2013 Residential Single-family Maximum	Mar. 31, 2013 Residential Multifamily	Mar. 31, 2012 Residential Multifamily	Mar. 31, 2013 Residential Multifamily Minimum	Mar. 31, 2013 Residential Multifamily Midrange	Mar. 31, 2013 Residential Multifamily Maximum
Non-Covered loans receivable disclosures
Accrued interest on covered and non-covered loans receivable	$ 84,200,000	$ 76,800,000
Covered and non-covered loans receivable pledged to secure borrowings from the FHLB and the Federal Reserve Bank	9,010,000,000	8,880,000,000
Number of units of residential property securing fixed and adjustable rate first mortgage loans					1	4
New first mortgage loans originated							$ 263,100,000	$ 220,400,000			$ 50,300,000	$ 17,200,000
Adjustable rate mortgage, term of initial fixed interest rates													6 months	3 years	5 years
Loans to value ratio (as a percent)										65.00%
Ratio of mortgage loans with interest-only features to total mortgage loans within same portfolio category (as a percent)							1.00%		1.00%
Ratio of mortgage loans with variable payment option features to total mortgage loans within same portfolio category (as a percent)			1.00%	1.00%
Number of loans negatively amortizing	0	0